Scalability

Microservices should be designed to be independently scalable. If we need to increase how many requests we can handle or how many records we can hold, we should do it in isolation. We should avoid that, due to a coupling on the architecture; the only way to scale our application is scaling several components together or through the system as a whole.

Let's go back to the original SoA application example and handle a scenario where we need to scale our offers capability:

Even if what we need to scale is our offer capability, due to the coupling of the system, we need to do it as whole. We will increase how many instances of the presentation and business layer we have, and we increase our database either with more instances or with a bigger database. Probably, we may need to also update some of those servers as the resources that they require will increase. In a microservices architecture, we could just scale the elements that are needed. Let's view how we could scale the same application using microservices:

We have just increased what was required for the offers' capability and to keep the rest of the architecture intact, we need to consider that in microservices, those servers are smaller and don't need as many resources due to their limited scope.

We will review more about this topic in the Cloud Native microservices section of this chapter.